CD73 is expressed on invading T lymphocytes in the inflamed peripheral nerve

SARS-CoV-2 and Guillain-Barré Syndrome: Lessons from Viral Infections

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is responsible for the COVID-19 pandemic. COVID-19 has a broad clinical spectrum from asymptomatic patients to multiorgan dysfunction and septic shock. Most of the common symptoms of COVID-19 are classified as respiratory disorders, but some reports show neurological involvements. During the COVID-19 pandemic, a case series of neurological complications, such as Guillain-Barré syndrome (GBS), were reported. GBS is a neuroimmune disorder with acute inflammatory radicular polyneuropathy in different parts of the peripheral nerve. Some studies have reported GBS as an inflammatory neuropathy related to various viral infections, such as cytomegalovirus (CMV), Epstein-Barr Virus (EBV), herpes simplex virus (HSV), human immunodeficiency virus (HIV), influenza, and Zika virus. There are some immunomodulation approaches for the management of GBS. Studies have evaluated the effects of the various therapeutic approaches, including intravenous immunoglobulin (IVIG), plasma exchange (PE), complement inhibitors, and corticosteroids to regulate overactivation of immune responses during GBS in experimental and clinical studies. In this regard, the possible association between GBS and SARS-CoV-2 infection during the outbreak of the current pandemic and also the mentioned therapeutic approaches were reviewed.

A single peri-sciatic nerve administration of the adenosine 2A receptor agonist ATL313 produces long-lasting anti-allodynia and anti-inflammatory effects in male rats

Neuropathic pain is a widespread problem which remains poorly managed by currently available therapeutics. Peripheral nerve injury and inflammation leads to changes at the nerve injury site, including activation of resident and recruited peripheral immune cells, that lead to neuronal central sensitization and pain amplification. The present series of studies tested the effects of peri-sciatic nerve delivery of single doses of adenosine 2A receptor (A_2aR) agonists on pain and neuroinflammation. The data provide converging lines of evidence supportive that A_2aR agonism at the site of peripheral nerve injury and inflammation is effective in suppressing ongoing neuropathic pain. After A_2aR agonism resolved neuropathic pain, a return of pain enhancement (allodynia) was observed in response to peri-sciatic injection of H-89, which can inhibit protein kinase A, and by peri-sciatic injection of neutralizing antibody against the potent anti-inflammatory cytokine interleukin-10. A_2aR agonist actions at the nerve injury site suppress neuroinflammation, as reflected by decreased release of interleukin-1β and nitric oxide, as well as decreased sciatic expression of markers of monocytes/macrophages and inducible nitric oxide synthase. Taken together, the data are supportive that A_2aR agonists, acting at the level of peripheral nerve injury, may be of therapeutic value in treating chronic pain of neuroinflammatory origin.

Inflammatory neuropathies: pathology, molecular markers and targets for specific therapeutic intervention

Inflammatory neuropathies encompass groups of heterogeneous disorders characterized by pathogenic immune-mediated hematogenous leukocyte infiltration of peripheral nerves, nerve roots or both, with resultant demyelination or axonal degeneration or both. Inflammatory neuropathies may be divided into three major disease categories: Guillain-Barré syndrome (particularly the acute inflammatory demyelinating polyradiculoneuropathy variant), chronic inflammatory demyelinating polyradiculoneuropathy and nonsystemic vasculitic neuropathy (or peripheral nerve vasculitis). Despite major advances in molecular biology, pathology and genetics, the pathogenesis of these disorders remains elusive. There is insufficient knowledge on the mechanisms of hematogenous leukocyte trafficking into the peripheral nervous system to guide the development of specific molecular therapies for immune-mediated inflammatory neuropathies compared to disorders such as psoriasis, inflammatory bowel disease, rheumatoid arthritis or multiple sclerosis. The recent isolation and characterization of human endoneurial endothelial cells that form the blood-nerve barrier provides an opportunity to elucidate leukocyte-endothelial cell interactions critical to the pathogenesis of inflammatory neuropathies at the interface between the systemic circulation and peripheral nerve endoneurium. This review discusses our current knowledge of the classic pathological features of inflammatory neuropathies, attempts at molecular classification and genetic determinants, the utilization of in vitro and in vivo animal models to determine pathogenic mechanisms at the interface between the systemic circulation and the peripheral nervous system relevant to these disorders and prospects for future potential molecular pathology biomarkers and targets for specific therapeutic intervention.

Nerve biopsy in chronic inflammatory neuropathies: in situ biomarkers

We collected the evidence for potential biomarkers in nerve biopsies that might be of use in diagnosis, assessment, or treatment response in chronic inflammatory demyelinating polyneuropathies (CIDPs). We performed a literature search in PubMed from 1965 to May 2010 using the key words (["chronic inflammatory polyneuropathy" or "polyradiculoneuritis" or {"chronic and neuritis"}] and "nerve biopsy") and searched manually within these references for relevant publications related to the subject. Twenty references gave information about potential biomarkers for CIDP. Evidence of demyelination alone is not specific for CIDP, but may support the diagnosis in the context of a typical clinical pattern. Although the total numbers of inflammatory cells do not distinguish well between CIDP and non-inflammatory neuropathies, the pattern of macrophage clusters around endoneurial vessels may be a simple marker of inflammation with good sensitivity and specificity. Immunohistochemistry for matrix metalloproteinase-9 may be useful for the distinction of inflammatory and non-inflammatory neuropathies. Microarrays which give a complex pattern of up- and downregulated genes also show promise for developing a biomarker. Immunohistochemistry on sural nerve biopsies has the potential to distinguish inflammatory from non-inflammatory neuropathies. More research is needed to establish the diagnostic validity of specific markers and of gene expression studies and to test whether they can distinguish between subtypes of inflammatory neuropathies.